It started Monday morning as a call from a gas station clerk in Mandeville to police about an abusive customer. But it quickly escalated, and by the time officers arrived, it had turned into a fatal shooting. The customer, 42-year-old Shawn Breland, lay in an aisle, shot three times in the chest and stomach.

His shooter, another customer who has not been identified, was waiting for police, having reholstered the .40-caliber handgun that fired the fatal shots.

Several hours later, police announced they had released the shooter without arresting him.

Ron Ruple, assistant chief of the Mandeville Police Department, said evidence from the scene, including statements from witnesses, video evidence and the shooter’s own account, pointed to a justifiable act of self-defense.

The incident began when Breland made a purchase at the Shell station at 3959 La. 22 in Mandeville. He berated the clerk, including the use of racial slurs, Ruple said.

The clerk ordered Breland to leave and threatened to call police. Breland did leave but returned to the store, becoming more aggressive, a pattern he repeated several times, Ruple said.

The clerk called police about 10:15 a.m.

The shooter, meanwhile, tried to assist by urging Breland to leave the store. A firearms instructor, he was wearing his gun in a holster on his hip, Ruple said.

Breland walked out again but then returned and threw what appeared to be potato chips at the clerk. The shooter followed Breland outside to get the license plate from Breland’s white minivan. Breland got out of the minivan and physically attacked the shooter, Ruple said.

The shooter drew his weapon and ordered Breland back, then went back into the store in an attempt to get away, Ruple said. But the 6-foot-1, more than 200-pound Breland followed him, pushing and grabbing for the gun, Ruple said.

The shooter backed into a corner and ordered Breland to stop, saying he would shoot him if he didn’t. When he didn’t, the shooter fired a single shot into Breland’s midsection, but Breland still didn’t stop, Ruple said. The shooter then fired two more shots.

St. Tammany Parish Coroner Charles Preston said Breland died from several rounds fired into his torso. An autopsy will be performed Tuesday and toxicology results collected.

Police cleared the scene in the early afternoon, and workers, who refused to be interviewed, could be seen carrying cleaning supplies into the store. The shooter declined an interview request from WWL-TV’s Ashley Rodrigue.

Mandeville police are handling the investigation, which they will refer to the District Attorney’s Office for a decision on whether to file charges.

The fatal shooting is Mandeville’s first since August 2011, when Joshua Roberson shot and killed his girlfriend, Tabitha Ross, in his Adair Street home, Ruple said.

In June 2013, a man was shot on the Tammany Trace during a drug deal, but he survived.

Follow Faimon A. Roberts III on Twitter, @faimon.